dma-buf/udmabuf: skip redundant cpu sync to fix cacheline EEXIST warning

{
  "id": "7edd518082bc35e755afab80684b443086bbea6eb1f2b123b3aa6e3dc7a3914c",
  "url": "https://osv.dev/vulnerability/CVE-2026-64590",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "dma-buf/udmabuf: skip redundant cpu sync to fix cacheline EEXIST warning",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: dma-buf/udmabuf: skip redundant cpu sync to fix cacheline EEXIST warning When CONFIG_DMA_API_DEBUG_SG is enabled, importing a udmabuf into a DRM driver (e.g. amdgpu for video playback in GNOME Videos / Showtime) triggers a spurious warning: DMA-API: amdgpu 0000:03:00.0: cacheline tracking EEXIST, \\ overlapping mappings aren't supported WARNING: kernel/dma/debug.c:619 at add_dma_entry+0x473/0x5f0 The call chain is: amdgpu_cs_ioctl -> amdgpu_ttm_backend_bind -> dma_buf_map_attachment -> [udmabuf] map_udmabuf -> get_sg_table -> dma_map_sgtable(dev, sg, direction, 0) // attrs=0 -> debug_dma_map_sg -> add_dma_entry -> EEXIST This happens because udmabuf builds a per-page scatter-gather list via sg_set_folio(). When begin_cpu_udmabuf() has already created an sg table mapped for the misc device, and an importer such as amdgpu maps the same pages for its own device via map_udmabuf(), the DMA debug infrastructure sees two active mappings whose physical addresses share cacheline boundaries and warns about the overlap. The DMA_ATTR_SKIP_CPU_SYNC flag suppresses this check in add_dma_entry() because it signals that no CPU cache maintenance is performed at map/unmap time, making the cacheline overlap harmless. All other major dma-buf exporters already pass this flag: - drm_gem_map_dma_buf() passes DMA_ATTR_SKIP_CPU_SYNC - amdgpu_dma_buf_map() passes DMA_ATTR_SKIP_CPU_SYNC The CPU sync at map/unmap time is also redundant f",
    "evidence": "osv:CVE-2026-64590",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.10.266",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "5.15.217",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.1.184",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.148",
            "evidence": "/affected/1/ranges"
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          {
            "value": "6.12.96",
            "evidence": "/affected/1/ranges"
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          {
            "value": "6.18.39",
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            "value": "7.1.4",
            "evidence": "/affected/1/ranges"
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        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-64590",
      "aliases": [
        "CVE-2026-64590"
      ],
      "affected": [
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                  "fixed": "01126abc11bcc6a45b664293b0b5df715be911d7"
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                  "fixed": "dd7f1e572f44d3d039dc77e3989f537196c3bf52"
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              "type": "ECOSYSTEM",
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                {
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            "ecosystem": "Linux"
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      ],
      "modified": "2026-10-28T02:30:48.507849566Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/01126abc11bcc6a45b664293b0b5df715be911d7",
        "https://git.kernel.org/stable/c/0449a6583c0ee76778d314e4e82f166fc97fa9d8",
        "https://git.kernel.org/stable/c/0db56e7eae932f8e2f3eb44ad1a63633d8f504f8",
        "https://git.kernel.org/stable/c/34696563461c9a23177feb6d8aff43f4c0510278",
        "https://git.kernel.org/stable/c/4a7c644e632741c2a3116a0d3da6c11de957a6ba",
        "https://git.kernel.org/stable/c/504e2b4ab97a51d56d966cd36d0997ad30b65b2d",
        "https://git.kernel.org/stable/c/d6552f5cff795d60e629f37513ecf23d88fd2f82",
        "https://git.kernel.org/stable/c/dd7f1e572f44d3d039dc77e3989f537196c3bf52",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64590.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-64590",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64590.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-64590",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 516737,
  "published_at": "2026-08-06T07:13:47.888+00:00"
}